Heat transfer

ABSTRACT

A heat transfer assembly is disclosed which comprises at least one wall ( 1, 2, 3 ) which is adapted to separate a first fluid at a first temperature from a second fluid at a second temperature, and at least one fibre member ( 6, 7, 8, 9 ) or plurality of them, each fibre member ( 6, 7, 8, 9 ) including at least one elongate fibre which extends substantially axially along the fibre member ( 6, 7, 8, 9 ) from the first fluid through the wall ( 1, 2, 3 ) and into the second fluid whereby in use heat is transferred from the first fluid to the second fluid or vice versa, and the entire heat transfer assembly or a part of it is assembled as a single unit by sewing/weaving/stitching technique.

[0001] This invention relates to improvements in heat transfer, and inparticular but not exclusively to a group of improved assembliesincluding heat exchangers and heat sinks which have been developed as aresult of research into certain problems that effect this group ofassemblies.

[0002] Traditionally heat exchangers and heat sink devices have beenfabricated from metals or their alloys. These materials havetraditionally been used because of their good thermal conductivity andthe fact that they are robust and easy to fabricate into rigidassemblies. Copper and aluminium are typically in use, and have thermalconductivity's of between 200W/mK and 380W/mK. The main disadvantage hasbeen that the materials are highly susceptible corrosion and relativelyheavy.

[0003] It has also recently been proposed that heat exchangers areproduced in ceramic materials. These materials do not corrode in humidoperating environments but are brittle and very difficult to work.

[0004] Advances in composite material technology has resulted in theproduction on commercial scales of non-metallic materials that haveexcellent mechanical and thermal properties and also low density. Forexample carbon fibres are available that have thermal conductivity's ofin excess of 2000W/mK whilst retaining a density lower than that ofaluminium.

[0005] To date, the only attempts to incorporate these new materialsinto heat transfer assemblies, such as heat exchangers, have been to usethe same processes that have been developed for metal designs. Forexample, this has simply involved the reproduction of a commerciallyavailable plate heat exchanger using plates of composite materials. Theexchanger comprises wavy sheets of composite material inserted intochannels defined between walls of composite material. Unfortunately, dueto the need for thermal transfer between the sheets and the walls manyof the potential benefits of composite materials are lost. Stressesinduced between the fins and the walls due to the bonding material mayalso result in premature failure.

[0006] The applicant has appreciated that prior art heat exchangers andheat sinks and the like can be improved by using composite materials,such as carbon fibre, in a different way to that previously consideredpossible.

[0007] In accordance with a first aspect, the invention provides a heattransfer assembly which comprises at least one wall which is adapted toseparate a first fluid at a first temperature from a second fluid at asecond temperature, and a plurality of fibre members, each fibre memberincluding at least one elongate fibre which extends substantiallyaxially along the fibre member from the first fluid through the wall andinto the second fluid whereby in use heat is transferred from the firstfluid to the second fluid.

[0008] By providing for one or more fibres to extend through the wall(s)of the heat exchanger there is no efficiency loss that is present whenthe fibres must transfer heat energy through the walls via a bondingmedia as in the prior art. This enables the unidirectional heatproperties of fibres to be exploited.

[0009] The resistance of the heat transfer assembly to pressure withinthe channels is increased because the fibre members pass through the oreach wall. The fibre members also produce turbulence in the channelsthat improves heat dissipation. It also allows the length of the fluidreceiving channels to be reduced making for a more compact andlightweight assembly.

[0010] The first and second fluids may be received within respectivefirst and second channels provided on opposing sides of the wall.

[0011] A number of walls may be provided. A stack of substantiallyparallel plates defining the walls, may be provided with a channel beingdefined between adjacent walls. For example, three parallel channels maybe provided which are defined by a stack of two plates disposed oneabove the other. The fibre members may be provided which extendcontinuously through all the walls or fibre members may be providedwhich only extend through a single wall between two channels.

[0012] The first and second fluids may comprise different fluids, forexample a gas and a liquid or different liquids.

[0013] Each fibre member may comprise a number of fibres to form aligament or fin or other structural element which adds to the rigidityof the finished structure. The thickness and shape of the fibre membersis not limited.

[0014] In accordance with a second aspect, the invention provides a heattransfer assembly adapted to transfer heat between a first fluid at afirst temperature and a second fluid at a second temperature, in whichthe heat transfer assembly comprises a fibre structure produced byweaving and/or sewing and/or stitching of fibres.

[0015] The heat transfer assembly, which may be produced in accordancewith the teachings of any of the other aspects of this invention may beentirely fabricated from fibres by stitched, woven or sewn together.Subsequently, said entire fibre structure may be impregnated with anysuitable matrix material or several materials, including ceramics suchas silicon carbide, carbon-carbon, metals and non-metals by any suitableprocesses such as material infiltration, chemical vapour deposition(CVD), metal casting, or any other. The invention provides anopportunity to weave/sew/stitch the entire fibre structure and use it oraccommodate it with any matrix including carbon-carbon and/or hightemperature ceramics, metal, or other high thermal conductance material,which have much better thermal properties compared to a plastic or resinmatrix. The thermal conductivity of the matrix is important because heatshould be conducted from single fibres through matrix into fluids.

[0016] When, optionally, impregnated with a matrix material thisprovides additional structural rigidity. However, by selectingappropriate fibres such as carbon fibres it is possible to produce anassembly which is self supporting without the use of a matrix material.

[0017] One or more of the fibres forming the fibre members may be woveninto or stitched into one or more of the walls. Thus, some fibres in thefibre members may pass through the walls whilst others are stitched orwoven into the walls to increase the strength of the assembly underpressure.

[0018] If suitable fibres, such as carbon fibre, are used, the structuremay be self-supporting without the need for additional resin or matrixmaterial.

[0019] This produces an integrated construction which, when pressurised,is able to hold its shape without bonding of the fibre members to thewalls.

[0020] Of course, the structure may still be impregnated with anymatrix, not limited to resin, after the weaving and/or securing of thefibres to form the walls and fibre members.

[0021] The heat transfer assembly may comprise a heat exchanger.

[0022] Compared to the prior art, the invention provides an opportunityto weave/sew the entire fibre structure and then accommodate it for anapplication and, if needed, filled with any matrix includingcarbon-carbon and/or high temperature ceramics, metals or other matrix,which have much better thermal properties compared to a plastic/resinmatrix, which can be applied for some applications. The thermalproperties of matrix are crucial for many applications. The said fibrestructure may form the basic structure of any of the following aspectsof the invention.

[0023] In accordance with a third aspect, the invention provides a heatradiating assembly comprising a heat source, one or more walls definingat least one channel, and one or more fibre members which extend throughthe wall or walls from the heat source to the channel whereby in useheat from the source is radiated from the fibre members into thechannel.

[0024] As for the first aspect of the invention the fibre members passthrough the walls which provides excellent thermal efficiency as well asresulting in a strong light weight structure.

[0025] The heat source may comprise a hot fluid or other heated body.

[0026] For example, the heat source may comprise an integratedelectronic circuit such as provided on a silicon chip or an electroniccomponent such as a transistor.

[0027] In a further alternative the heat source may comprise a substrateonto which one or more electronic components may be thermally mounted.Suitable components include power transistors such as IGBT transistorsor FET transistors. Of course, the substrate may be omitted and thecomponents may be mounted directly onto the one or more walls.

[0028] The resulting radiator assembly differs from those known in theprior art in that a woven fibrous structure can be produced usingnon-metallic fibres for improved heat radiation when compared tometallic members. The fibres passing through the walls as opposed tobeing bonded to the walls further increases efficiency.

[0029] The body or object to be cooled may be formed integral to theheat transfer assembly. Hence, at least part of the body to be cooled(or heated) may be fabricated from the same materials as the fibremembers. The body and the fibre members may then be fabricated atsubstantially the same time, i.e. in the same factory or site in aseries of operations or a single operation.

[0030] One proposed use of the invention is as a heatsink for anelectronic processing device, such as the pentium class of processorsfor microcomputers. The heat transfer assembly may be bonded directlyonto one face of a processor of this type, or indeed other similarcircuitry.

[0031] Thus, in accordance with a fourth aspect, the invention providesan electronic circuit provided on a substrate, the substrate including aplurality of fibre members extending therefrom through which heatgenerated by the substrate can be dissipated.

[0032] By providing a substrate (which forms one “wall” of the precedingaspects of the invention) with integral fibre members an improvedcooling effect can be achieved as the need for a thermally conductivebond between the heat sink (i.e. the fibre members) and the circuitsubstrate is eliminated.

[0033] Integrated electronic circuits commonly referred to as microchipstypically comprise a crystal-polycrystal semiconductor on which thecircuitry is etched. Then several layers are usually added between thesemiconductor and a metallic/ceramic heat sink in order to accommodatethe differences in the thermal expansion of materials. All of this ispackaged within a protective casing. The need for these layers can beeliminated and the crystal or other semiconductor structure can directlycontact the fibres, which are embedded at least at one end in asubstrate or even in a semiconductor itself.

[0034] It is preferred that the material of the composite structure isselected to have the same coefficient of expansion as the circuit to becooled. For example, for silicon and silicon carbide electronics siliconcarbide or silicon could be used. Any kind of matrix could be used iffibres with extremely low thermal expansion determine the thermalexpansion of the composite.

[0035] It is known that silicon upon which microelectronics circuits aretoday formed has a very low coefficient of expansion. Carbon fibres alsohave a low coefficient and so the substrate can be conveniently formedfrom carbon fibres, optionally in a binding material with an optionalmatrix. One face of the composite substrate may be polished and thedevice bonded/deposited in position onto the polished surface.

[0036] Alternatively the material upon which the microelectronicscircuit is formed may be deposited directly onto the substrate thatsupports the fibre members. A suitable layer of material may be appliedusing ion beam epitaxial technology, thin-film semiconductor technology,or carbon-carbon since recently some modification of carbon was found tobe good semiconductor, or other technology.

[0037] Indeed, it is also conceived that the material upon which thecircuit is to be etched could be deposited directly onto afibre/rod(tube) member or/and fibre-composite plate to produce anon-planar substrate for circuitry with excellent cooling.

[0038] It is envisaged that fibre members may comprise the substrate anda semiconductor itself. Also fibres can be fabricated from existingsemiconductors such as silicon carbide, silicon or any other suitablematerial.

[0039] The fibre structure, which comprises heat conductive fibremembers (such as rods or loops) integrated into the substrate have anenhanced beat transfer area with much more efficient heat exchange ifcompared to a planar panel structure.

[0040] One or more of the fibres of the fibre members may encase, eitherwholly or partially the circuit to be cooled. By providing electricallyconductive fibres it is possible to protect the circuit from externalelectromagnetic effects/impulse (EMI) by forming a fibre layer screenand connecting the fibres to a suitable potential such as an earthpoint.

[0041] By providing a fibre structure, which can by analogy beconsidered to comprise a fur of coated conductive fibres on thesubstrate a more efficient conversion can be achieved when compared witha planar panel structure.

[0042] In the heat transfer assembly of the first, second and thirdaspects of the invention or the integrated structure of the fourthaspect each or selected ones of the fibre members may have an electricalcharge applied to it/them.

[0043] The application of an electrical charge can be used to controlthe orientation of the or each fibre relative to adjacent fibres and/orrelative to the wall or walls of the assembly.

[0044] Of course it will be readily appreciated that the application ofan electrical charge is not limited to heat assemblies in accordancewith either of the first three aspects of the invention.

[0045] Therefore, in accordance with a fifth aspect the inventionprovides a heat transfer assembly that comprises at least one wall whichis adapted to define a wall of at least one fluid receiving channel anda plurality of fibre members which each extend through the wall and intothe channel whereby in use heat is transferred from a first side of thewall to the fluid in the channel and means for applying an electricalcharge to the or each fibre structure to control the orientation of eachfibre structure relative to the wall.

[0046] In a simple arrangement the fibre members of any of the firstfour aspects of the invention may all be subjected to the same charge sothat they repel one another to maintain substantially even spacingbetween the fibre members. This enables non-rigid members to be employedwhilst maintaining dense spacing of the fibre members and will provideoptimal exposure of each fibre to the fluid.

[0047] In an alternative, if similar charges are applied to adjacentfibres they will attract one another causing the fibre to close up asthe fibres try to clump together. This will reduce the spacing betweenfibres and so reduce the efficiency of heat transfer.

[0048] The performance of the heat transfer assembly may therefore bemodified by applying different charges to the fibres under the controlof a control unit.

[0049] It will be appreciated that the fibre members must be adapted tomove relative to the substrate. This can be achieved by providingflexible fibre members or at least having flexibility in place where thefibre members and the substrate congregate. The fibre members need notbe completely flexible, and may comprise both flexible and rigidportions. A mixture of the various types of fibre members, some rigidsome flexible, may also be provided in a single structure.

[0050] By varying the electrical charge applied to one or more of thefibre members it may be possible to change the angle at which aparticular fibre is oriented. This may comprise applying differingpolarities and magnitudes of charge to one or more of the fibre members.Thus, tuning of an antenna could be performed. At the same time saidantenna can be a heat transfer cooling/heating system.

[0051] An example of such a structure within the scope of this aspect ofthe invention is the provision of a fibre bundle comprising a number offibre members which are bonded to each other at both ends of the fibrebundle but are free therebetween. After being electrically charged, saidstructure will form spheroid/bottle like object. Such structures can beused as electrically controlled antennas/radiators or electricallycontrolled shifting mechanism for satellites.

[0052] It has been found that electrically charging the fibres in achannel with either negative/positive potential or an alternatingpotential can enhance the operation of the heat transfer assembly,increasing convection heat transfer from surfaces to fluid and viceversa. In such assembly dielectric or gas fluid is disturbed bygenerated electrical charges or the applied electrical field disturbsthe dipole structure of a fluid, thus destroying thermal layers of fluidelectro-mechanically and improved conditions of a heat transfer occur.

[0053] The walls may be made of electrically non-conductive materialwhilst the fibre members are conductive or vice versa. One or more ofthe walls and/or the fibre members may be used as electrodes. Forexample, carbon fibres and cloth could be used. One or more of the wallsmay also be made of an electrically insulating material, fibrous ornon-fibrous.

[0054] In one advantageous arrangement, alternate walls, i.e. opposingwalls of a channel may be held at different potentials.

[0055] In the case where the heat transfer assembly is adapted tocontact a body or object to be cooled (or heated) an electricallyinsulating layer may be provided. The insulation could be deposited ontothe end of the fibres of the fibre members if they are conductive, orthe surface of the fibre members after assembly and/or of the walls. Theinsulation may partially or entirely cover the fibre members.

[0056] The provision of the electrical potential to a fibre structuremay also be used in other applications. It will be appreciated that thebenefits are not restricted to heat transfer assemblies.

[0057] Hence, in accordance with a sixth aspect the invention provides alight guiding assembly comprising a substrate having a plurality offibre members extending therefrom, in which each fibre structurecomprises at least one optical fibres which is adapted to guide lightfrom the end of the fibre nearest the substrate to the other end of thefibres, and control means for applying an electrical charge to the fibremembers to control the direction in which light is guide by the opticalfibres.

[0058] In a further (seventh) aspect, the invention provides a solarconverter adapted to convert light incident upon the panel intoelectrical energy and which comprises a substrate and a plurality offibre members which extend from the substrate, the fibre members havingone or more layers of photovoltaic material.

[0059] In both the sixth and seventh aspects of the invention, the lightmay be adapted to pass along only a selection of the optical fibres inthe assembly.

[0060] The light guiding structure may include a light source which isadapted to produce light that passes along the optical fibres. The lightsource may be connected to the substrate.

[0061] In accordance with an eighth aspect the invention provides aheatsink assembly for a device to be cooled which comprises a hollowbody having first and second open ends, an outer surface and an innersurface and which is provided with a plurality of fibre members thatradiate generally from a first interior surface of the body across theinterior of the body to contact the interior surface of the body in adifferent area, and in which the body is adapted to contact the deviceto be cooled substantially at the first area so that the fibreassemblies are in thermal contact with the device.

[0062] Providing a heat sink in accordance with the eighth aspect of theinvention heat is transferred along the fibre members into the hollowbody where it can be passed into cooling fluid flowing through the body.

[0063] The fibre members may be in direct or indirect thermal contactwith the device to be cooled. They may therefore pass through the bodyat the first area if direct contact is desired.

[0064] The heat sink may be thermally bonded to the device.

[0065] The heat sink may have dimensions compatible with amicroprocessor chip. It may have a generally clamshell form which isgenerally tubular with the first area of the body defining a flattenedbase portion which can be placed in contact with the device to becooled.

[0066] The body may therefore comprise a substantially cylindricalsleeve of material through which fluid can be passed. The material maybe a fibrous material which may be woven. It may be impregnated with abonding resin to form a rigid composite structure, or may be a plasticsor resinous material.

[0067] A fan may be provided which is attached to the heatsink towardsone end of the hollow body, or perhaps within the hollow body. The bodymay therefore define a cowling for the fan and act as a support for thefan.

[0068] The fan may comprise an electrically powered device.

[0069] Of course, it is possible to modify the preceding aspect of theinvention so that a semiconductor material onto which an electroniccircuit can be formed is deposited directly onto first of the body.

[0070] More than one device to be cooled may be thermally connected tofirst area of the body. This area can be extended, more fibre membersinstalled, and thus more devices connected to be cooled. For example,they may be spaced around the outside of the body in several areas.Fibre members may then radiate from each of these areas across theinside of the body.

[0071] In accordance with a yet further (ninth) aspect of the invention,an evaporator/condenser is provided by combining a heat transfer devicein accordance with the first aspect of the invention with a porouscapillary structure sandwiched between the first and second channels.

[0072] The above embodiments all have the common feature of at least onefibre member and in many arrangements one or more walls. These featuresmay take many forms.

[0073] In most cases it is an important feature of the invention thatthe fibre members have a high thermal conductivity. This can be achievedthough the use of fibres having a conductivity of at least 200W/mK. Forexample carbon fibres may be used which have a conductivity of around2000W/mK.

[0074] One or more of the fibre members may include surface perforationsor depressions. The fibre members may include metallic or other fibresto conduct electricity. Other suitable fibres include carbon thread, orsilicon dioxide or sapphire fibres. A mixture different fibre types maybe provided as part of a single fibre member.

[0075] A benefit of providing the depressions is that the surface areaof the fibres is increased and so the heat transfer properties of thefibres are improved.

[0076] The surface and structure of fibre members, walls and structuralmembers may be fabricated in order to control heat transfer features onmacro and micro levels: 1) with different roughness and 2) differentporosity and size of pores and 3) different directions of pore channelspores on micro level, and on macro level—fibre members may includesurface perforations, depressions, grooves, outstanding fibres, etc.

[0077] Despite superior thermal conductivity the fibre heat transferstructure has much higher heat transfer surface, therefore effectivenessof heat transfer in fibre structures can be much higher than inconventional metal structures. This is simply true for single-phase heattransfer. For phase change heat transfer this advantage can be muchhigher if the composite structure is properly designed.

[0078] In order to enhance heat transfer in the boiling process, thesurface on which this process occurs should be increased and conditionsfor nucleation site generation improved. At the same time duringcondensation, condensed fluid should be taken away from the heatexchange surface of condensation. Two of the many advantages of theinvented fibre structures are that the surface of the fibre issubstantially larger than any state-of-the-art heat transfer surface,plus, the surface of the fibre could be easily enhanced and improved forboiling nucleation purposes, for example, chemically. The carbon fibresurface can be “activated” by oxidisation and nature of “pits” is verysuitable for nucleation sites. Moreover, fibres easily form capillarychannels, which collect working fluid inside leaving other surfaces dryfor better condensation. At the same time, some bigger channels shouldbe provided for fluid transportation. Thus, said fibre members of thesaid heat exchange assemblies can be designed using all said conditionsand points.

[0079] One or more of the fibre members common to each of the aboveaspects of the invention may be charged electrically.

[0080] One or more of the fibre members may be adapted to form at leastone capillary channel for transporting cooling/heating liquid to theobject of cooling/heating or from the object heating by capillaryaction. This capillary structure forms a wick structure for capillarythermal management system. A variety of different material fibres withdifferent internal structure could comprise a wick.

[0081] Heat transfer assemblies including capillary cooling channels usedesiccating or absorbing heat energy and capillary action of the wickfor transport working fluid. These are passive systems and don't havemoving parts. They don't require additional energy for transportingworking fluid, are quiet, and are extremely reliable.

[0082] In one arrangement, it is envisaged that a fibre member defininga capillary channel may be attached to one wall of the fibre heatexchange assembly.

[0083] Alternatively, the or each wall, structural member, or fibremember of the heat transfer assembly may comprise a capillary structure.A plurality of walls, structural members or fibre members form acapillary structure which can be used for transporting, by capillaryaction, working fluid which evaporates from the capillary structure(absorbing heat from the heat transfer assembly) or condenses on thewall, structural member, or fibre member, absorbing by capillarystructure (supplying heat to the heat transfer assembly)

[0084] The channel or channels of this heat transfer assembly can beopen and liquid can evaporate into its surrounding or space providingevaporative cooling, for example, for a space station escape module.Liquid can also condense on the walls, structural members and/or fibremembers of an open channel and be collected as, for example, watervapour from air. In most applications, one or more channels are closedand fibre capillary structure provides circulation of cooling fluid inthe system. In the closed channel capillary structure can occupy part ofthe channel for transporting liquid. Part of the channel or separatechannel has to be open for vapour circulation.

[0085] One or more walls of the channel or channels can be comprised ofa capillary structure, separating liquid channels from vapour channelsor it can be the wall of one channel attached to the object ofheating/cooling. The rest of the channel space may be used for vapourcirculation. The structural member in the channel can comprise thecapillary structure. It also can separate liquid and vapour channels,occupy part of the channel or form the channels inside of it. The fibremembers themselves can form the capillary structure if the distancebetween them or between fibres inside them is small enough to providethe capillary action or the internal structure of fibre can provide thecapillary action.

[0086] Also the capillary structure can be formed by a combination ofdifferent elements of the heat transfer assembly. As was mentionedabove, the fibre members can form the capillary structure, which willprovide the evaporating pumping head for circulating cooling fluid inthe system. If the distance between the walls is small enough it willhave sufficient capillary pumping pressure on the corners between thestructural member and the wall for circulation of cooling fluid. Varyingthe wall profile in one channel geometry can create a similar structure.

[0087] Where walls are provided to define one or more channels, thechannel(s) may be open sided, thus allowing heat from the heat source tobe radiated in a controlled manner through the fibres into the openchannel. Alternatively the channels may be closed sided. The ends of atleast one fibre member may terminate within the channel to allow heat topass into the fluid surrounding the entire fibre member and its end byconvection, conduction and radiation.

[0088] Composite materials are preferred for the fibre members and thewalls, such as a structure having carbon or silicon dioxide fibres,possibly in a resin. It is important that the fibres have a good thermal(e.g. very high or very low) conductivity at least axially with respectto the fibres.

[0089] Preferably one or more of the fibre assemblies comprises at leastone nonmetallic thread or ligament. The thread may comprise a carbonthread although many other materials having high thermal conductivitymay be used.

[0090] Alternatively, the fibre members may each comprise a plurality ofthreads or ligaments which are woven, threaded or bonded together toform a thicker structure than a single thread.

[0091] The or each wall may comprise a woven sheet of fibres. The fibresmay be the same as those used to form the fibre members or may bedifferent material. It is preferred that the fibres of the walls have alower thermal conductivity than those of the fibre members to reduceheat transfer between the fibre members and the walls.

[0092] It is envisaged that in at least one advantageous arrangement theapparatus comprises both walls and fibre members that are produced usingconventional weaving or sewing techniques. It is therefore not necessaryto include binding material (i.e. matrix) to hold the assembly together.It could therefore be entirely constructed by sewing or weaving ifdesired.

[0093] Stitches may be made by sewing a thread consisting of a singlestrand of fibre, which may be continuous or discontinuous, or bystitching using a thread made from multiple strands. Alternatively, thethreads may comprise braids or tapes made up of many strands.

[0094] Of course, the walls may be fabricated from non-fibrous materialssuch as polymeric resin, plastics material or ceramic material or someother material in some embodiments, or perhaps of combination of variousmaterials in one assembly.

[0095] A plurality of walls may be provided that define first and secondclosed channels down which the two fluids can be passed. The walls maybe parallel to one another or perhaps non-parallel.

[0096] The walls may be substantially planar or non-planar and may bedefined by opposing sides of one or more plates of fibrous material orpolymeric or plastics material. For example a structure comprising astack of generally rectangular walls may be provided, or the walls mayform a set of concentric, i.e. nested cylinders with the channelsdefined therebetween and the fluid flowing generally axially relative tothe cylinders. Other possible shapes are envisaged, i.e. triangular,polygonal.

[0097] The provision of concentric nested walls can be used toespecially good effect.

[0098] Thus, in accordance with a still further aspect the inventionprovides a heat transfer assembly for a gas turbine or the like in whichthe heat transfer assembly is in accordance with any one of thepreceding aspects of the invention and has at least three concentricallyarranged walls; a first inner wall, an intermediate wall and a secondouter wall defining at least two annular channels therebetween thatsurrounds at least a part of the gas turbine, one or more of the fibremembers passing through the intermediate wall to remove heat energy fromfluid within the channel.

[0099] This arrangement reduces the amount of space required whencompared with a remotely located recuperator. Furthermore, due to thehigh structural rigidity that can be achieved, weight savings can bemade as the heat transfer assembly may form a structural part of the gasturbine. It may form a structural casing surrounding the gas turbine.

[0100] As well as gas turbines, it will be appreciated that theinvention has other applications, for instance in cooling ovens or othertypes of engine.

[0101] In a refinement, an additional wall can be provided which isconcentric with the outer wall and which is adapted to define a furtherchannel that may receive fluid such as water. The heat energy extractedfrom the exhaust gas can then be used to heat the water.

[0102] It is preferred that the fibre members pass through all of thewalls to transfer heat from the hot exhaust gas into a cooling fluid andthen the water on opposing sides of the wall. One or more of the fibremembers may extend radially from one wall to a more outer wall. They maycomprise strips or fins and may be shaped to form an aerofoil.

[0103] In accordance with another aspect, the invention may provide agas turbine or other engine incorporating a heat transfer assemblyaccording to the preceding aspect of the invention.

[0104] In order to further improve heat transfer efficiency of theassembly, the cylindrical channels can be subdivided into smallerchannels by inserting a structural member or baffle that divides eachcylindrical channel into a number of subchannels. This may comprise acorrugated structure and may be fibre based.

[0105] The fibre sheets and/or the fibre members may be impregnated witha binding material to form a composite structure. This is advantageousin some situations as it enables a light and highly rigid assembly to beproduced. As is known in the art of composite material fabrication, theproperties of the heat exchanger may be altered by weaving or laying upthe fibres in more than one direction to control dissipation of stressin the assembly. The binding material may comprise a polymeric resinwhich may be applied to fibrous material after it has been woven intothe desired configuration defining the fibre members and the walls. Thisprovides the advantage that no glue is used to bond separate walls tothe fibre members and produces a single integrated assembly.

[0106] The binding material may be added to the fibres to produce thefinal composite assembly using carbon-carbon, chemical vapour depositionor plastic precursor techniques or other material infiltration.

[0107] The fibre members may be hollow and may be filled with apolymeric resin or other binding material after the assembly has beenfabricated to enhance its structural rigidity. Thus for example fibresmay be filled with ceramic material such as silicon carbide.

[0108] The fibre members may include a protective coating on the outersurface for contact with the fluid in the channels. The coating may, forexample, protect the fibres from corrosion.

[0109] The fibre members may extend through the walls substantiallyorthogonal, i.e. at ninety degrees to the walls. Thus provides excellentresistance to expansion stresses caused by the pressure of the fluid inthe channels.

[0110] Alternatively, the fibre members and the wall may define anobtuse or acute angle other than ninety degrees. One or more of thefibre members may subtend a different angle relative to the wallscompared to one or more of the other fibre members. Thus, the fibremembers may subtend a number of different angles relative to the walls.This arrangement increases the resistance of the structure to shearstresses, i.e. stresses that lie in the plane of the walls.

[0111] In a most advantageous arrangement, the fibre members may passthrough the walls so as to form a series of triangles criss-crossing thefirst and/or second or further channels. This effectively increases thestrength of the structure. When combined with binding material to form acomposite structure this enables the assembly to function as astructural element. A structural element or baffle may still be providedin this arrangement, and one or more of the fibre members may passthorough the baffle.

[0112] The provision of a criss-cross structure may be further enhancedby filling the area between the walls with a binding material to form asolid composite structure of great strength yet light weight.

[0113] The walls of the heat transfer assembly may define at least oneclosed channel. A reinforcing baffle may be provide within the channelwhich alternately contacts opposing walls of the channels to definecorrugations, which can define sub-channels.

[0114] The walls may be parallel or non-parallel to one another and maybe planar or non-planar.

[0115] The reinforcing baffle preferably comprises a wavy sheet that isprovided between the opposing walls of the closed channel. The sheet maybe fixed to one wall at its crests and to the other wall at its troughs.The fibre members extending through the walls may also extend throughopenings in the baffle.

[0116] The reinforcing baffle may be impregnated with a binding materialat the same time as the walls and/or fibre members.

[0117] The reinforcing baffle may be added before, during, or afterproduction of the walls of the channel. It may be bonded to the walls. Anumber of baffles may be provided between the walls. The corrugations inthe baffle may effectively divide the channel into a number of subchannels. Each subchannel may be used to contain fluids of differingtypes or at differing temperatures.

[0118] The or each of the fibre structure may have a uniform ornon-uniform cross section along its length such as a circular or oblatecross-section. The members may be spaced uniformly or non-uniformlythroughout the channels. For example, the members may comprise discreterods which are randomly placed in the channel or staggered with membersprovided at regular intervals. They may comprise elongate strips and maybe shaped as an aerofoil to minimise pressure drops as fluid flowsacross the fibre members. For example, the members may comprise discretecomposite or non-composite rods, which are placed in the channelaccording to some aerodynamic/heat exchange model or staggered withmembers provided at regular intervals. They may also comprise elongatestrips. In order to decrease pressure drop the fibre member can havevery special form, such as airfoil or other low drag geometry. The axleof the fibre member cross-section can be parallel to the flow direction,nonparallel, or orthogonal

[0119] Where the walls are circular, the fibre members may extendradially from the inner wall of a channel to its outer wall. Thesemembers may comprise thin strips which extend axially of the channel aswell as radially.

[0120] Where the heat transfer assembly includes at least two channels,a means may be provided for circulating the second fluid along thesecond channel and/or the first fluid along the first channel.

[0121] At least one of the channels may be open sided, for instance toallow cooling air to contact the fibre structures where they protrudeinto the open channel. Alternatively, the channels may be closed.

[0122] Means may provided for providing an electrical potential to theassembly to enhance the heat exchanging properties of the assembly.

[0123] One or more of the walls anlor the fibre members may therefore bemade electrically conductive material. For example, carbon fibres couldbe used. One or more of the walls may also be made of an electricallyinsulating material.

[0124] In one advantageous arrangement, alternate walls, i.e. opposingwalls of a channel may be held at different potentials.

[0125] By varying the electrical charge applied to one or more of thefibre members it may be possible to change the angle at which light isemitted from the fibres relative to the substrate. This may compriseapplying differing polarities and magnitudes of charge to one or more ofthe fibre members.

[0126] The invention as set out in accordance with the precedingparagraphs can be adapted to operate over a wide range of hightemperatures by choosing fibre materials that have a very low thermalexpansion coefficient. Conversely, this also allows them to be used withfluids at very cold temperatures. In traditional metal heat exchangers,for instance employing Inconnel alloys thermal stress have been found tocause failure of the joints needed to hold the structures together. Anassembly produced using suitable fibres, such as carbon fibres, byweaving or like processes overcomes these problems.

[0127] In accordance with yet a further aspect of the invention anelectronic device is provided which comprises a substrate, an electroniccircuit defined on the substrate and one or more optical fibres embeddedon or within the substrate with or without other fibres adapted todirect light onto one or more components of the microelectronicscircuit.

[0128] The light guiding fibres may be used to direct light onto thecomponents defined within the substrate to correct radiation damage ofthe components.

[0129] Looked at another way, this aspect may be a method of coolingand/or correcting the effects of radiation damage on the components of amicroelectronics circuit within a substrate by guiding light onto thecomponents through fibres that are integral with the substrate.

[0130] In accordance with a still further aspect the invention providesa structural material produced from fibres by weaving/sewing/stitchingusing fibres. The material may have a similar structure to corrugatedcardboard but exceeds the structural properties of corrugated cardboardthrough the use of advanced materials. Actually, several types of astructural material are envisioned within the scope of the invention.

[0131] The corrugated material/structure may comprise at least twowalls, and a plurality of fibre members, which may extend through thewalls substantially orthogonal to the walls. This produces a structurethat is extremely resistant to expansion stresses but not as resistantto shear stresses.

[0132] To improve the structure resistance of the structural material toshear stresses the fibre members and the wall may define an obtuse oracute angle other than 90 degrees.

[0133] One or more of the fibre members may subtend a different anglerelative to the walls compared to one or more of the other fibremembers.

[0134] The said structural/corrugated material can be also fabricatedwithout inside corrugated baffle but by filling the inside space betweenwalls by some material—for example some plastic such as polyethylene,resin, or rubber.

[0135] The corrugated baffle or the filling structural member fillingthe structure, as said above, can be made using porous materialincluding fibrous materials and used not only as structural materialwith the ability to work as the heat exchange structure with single ortwo-phase working fluid.

[0136] The filling material or the structural member could be thermallyinsulating as well as fibres of the said fibres assembly, and saidstructural material could be advantageous as a reinforced structuralthermal insulator. And vice versa, the similar structural material basedon high thermal conductivity fibres and filled with high thermalconductivity material, such as graphite felt, porous graphite or othercan be high thermal conductivity material with high mechanicalproperties.

[0137] Different variations and mixtures of said structural materialsmight be envisioned, such as the high thermal conductivity reinforcedmaterial with working fluids inside, which will participate in heatexchange process. The said structural/corrugated material can have alsonon-planar different shapes including tubes.

[0138] Any additional structural members like a baffle or fillingmaterial could be incorporated into the structural tube. Fibre members,which penetrate walls and structural members of the said tubes, can havedifferent angles between each other and with other parts of the tubes.

[0139] All said structural materials and all said in this art fibre heattransfer assemblies can have the residual stresses processed into thestructure during fabrication.

[0140] Said structural/corrugated carbon or other fibre basedmaterials/structures can be fabricated using orthogonal andnon-orthogonal to walls and other elements fibre members, and differentshape and directions structural members if they are elected to beinstalled.

[0141] All fibre and non-fibre members and elements of said structuralmaterials could be bonded to each other in proper places or not bonded.Prefabricated stress inside fibre members and structural members isoptional. All said structural materials have superior properties, whichcan be further enhanced by filling matrix.

[0142] The invention may provide a structural component of an aircraft,spacecraft or other vehicle comprising the above-defined structuralmember. This may be adapted to receive a cooling fluid to provide awhole-vehicle-cooling concept. It is envisaged that this could be usedto lower a vehicle or crafts thermal signature.

[0143] The fibre structures may be very flexible in shape. A pluralityof walls may be provided that define first and second closed channelsdown which the two fluids can be passed. The walls may be parallel toone another or perhaps non-parallel, circular or any other shapeincluding irregular shapes.

[0144] There will now be described by way of example only severalembodiments of the present invention with reference to the accompanyingdrawings of which:

[0145]FIG. 1 is a partial cross sectional view of a plate fibre heatexchange structure with fibre members structure constructed inaccordance with one aspect of the invention;

[0146]FIG. 2 is a partial cross sectional view of a modified plate heatexchanger with bonded/protected fibre members structure constructed inaccordance with one aspect of the invention;

[0147]FIG. 3 is a partial cross sectional view of a plate heat exchangerwith fibre members penetrating the structure not orthogonal to walls ofthe fibre heat exchange or the like structure constructed in accordancewith one aspect of the invention;

[0148]FIG. 4 is a perspective view of a different embodiment of a heatexchanger or the like in which a structural member/baffle divides asingle channel into sub-channels along which different fluids may bepassed;

[0149]FIG. 5 is a perspective view of a similar to previous embodimentof a heat exchange structure or the like in which structural members ormaybe one structural member/baffle divide two channels into sub-channelsalong which different fluids may be passed;

[0150]FIG. 6 is a cross sectional view of one fibre or structural memberof the fibre composite structure;

[0151]FIG. 7 is a partial cross sectional view of an embodiment of thefibre heat exchange structure or the like in which the fibre members arenot orthogonal relative to the plane of the plates with an installed instructural member filling an entire space between walls. The shownembodiment could be important for structural material applications;

[0152]FIG. 8 is a partial cross sectional view of an embodiment of thefibre heat exchange structure or the like in which the fibre members arenot orthogonal relative to the plane of the plates with an installed intwo structural members. One structural member/baffle, and otherstructural member filling an entire space between walls. Shownembodiment could be important for a structural material application;

[0153]FIG. 9 is a partial cross sectional view of an embodiment of thefibre heat exchange structure or the like in which the fibre members arenot orthogonal relative to the plane of the plates;

[0154]FIG. 10 is a perspective view of part of the fibre structureillustrated in FIG. 9;

[0155]FIG. 11 is an alternative embodiment of the fibre structureillustrated in FIG. 4 in which the structural member/baffle is porousand an entire structure comprises a capillary evaporator/condenser or aspecial structural material;

[0156]FIG. 12 is a cross sectional view of an embodiment of a fibre heatexchange structure or the like having cylindrical walls and fibremembers, which are orthogonal to cylindrical plates;

[0157]FIG. 13 is a cross sectional view of an embodiment of a fibre heatexchange structure or the like having cylindrical walls similar to thoseillustrated in FIG. 12, but with an installed reinforcing baffledividing a channel into sub-channels and fibre members which are notorthogonal relative to the walls;

[0158]FIG. 14 is an overhead view of a set of fibre members illustratingsome of the various possible spatial arrangement of the fibre memberswithin the heat transfer assembly;

[0159]FIG. 15 is an evolution of the fibre heat exchange structure intoa heat sink with partial cross sectional views of an embodiment of aheat sink in accordance with the present invention bonded to an objectto be cooled or heated, and with an embodiment of a heat sink with anobject to be heated/cooled deposited on a wall;

[0160]FIG. 16 is a partial cross sectional view of an embodiment of thefibre heat exchange structure, which comprises a heat sink in accordancewith the present invention bonded to an object to be cooled or heated;

[0161]FIG. 17 is a cross sectional view of an embodiment of a combineddevice to be cooled/heated and the heat sink in which heat conductingfibres are embedded within the device to be cooled;

[0162]FIG. 18 is a cross sectional view of an embodiment of a combineddevice to be cooled/heated and the heat sink in which heat conductingfibres are embedded within the device to be cooled with an electricalinsulation between the device and heat conducting fibres;

[0163]FIG. 19 is a partial cross sectional view of an embodiment of thefibre heat exchange structure, which comprises a heat sink in accordancewith the present invention bonded to an object to be cooled or heated asillustrated in FIG. 16, but with an electrical insulation layer betweenthe device and the heat sink;

[0164]FIG. 20 is an illustration of a heat sink, which comprises a fibreheat transfer structure attached to a device to be cooled; theembodiment defines channels along which heat transfer fluid is passed.The wall to which a device to be cooled/heated is bonded can be removedand the device can be a wall itself;

[0165]FIG. 21 is a modification of the heat sink of FIG. 16 in which acoating of protective and/or electrically insulating material isprovided;

[0166]FIG. 22 is a perspective view of an embodiment of the inventedheat sink of FIG. 19;

[0167]FIG. 23 is an illustration of a three dimensional micro-electroniccircuit deposited on the surface of fibres or other kind of high thermalconductivity members, for example, carbon rods and plates, integratedwith a heat sink in accordance with one aspect of the invention;

[0168]FIG. 24 is an illustration of a micro-electronic circuitintegrated with a heat sink and protected by fibre members from EMI inaccordance with one aspect of the invention;

[0169]FIG. 25 is a view of a heat sink with a cooling fan, which can beintegral with an object to be heated and/or cooled;

[0170]FIG. 26 is a view of an embodiment of the invented heat sink ofFIG. 25 with a different orientation of fibre members;

[0171]FIG. 27 is a perspective view of the invented heat sink of FIGS.25 and 26 with an integrated microchip shown;

[0172]FIG. 28 is an illustration of a still further embodiment of a heatsink design in which the fibre members are electrically charged, andsaid heat sink design can be used also as an antenna, thermalradiator/receiver a solar battery, a light reflector/receiver, etc. inaccordance with aspects of the invention;

[0173]FIG. 29 is an illustration of a still further embodiment of a heatsink design of FIG. 28 in which the fibre members are electricallycharged, but fibre members are bonded from both ends; said heat sinkdesign can be also used as a thermal radiator, an antenna, a solarbattery, a light reflector/receiver, etc. in accordance with aspects ofthe invention;

[0174]FIG. 30 illustrates a modified heat transfer assembly in which thefibre members that pass through the channels are electrically chargedand used as electrodes;

[0175]FIG. 31 is an alternative to an embodiment shown in FIG. 30 inwhich the walls of the channels are electrically charged.

[0176]FIG. 32 is a view of an embodiment of the invented heat sink ofFIG. 17 in which heat conducting fibres are embedded within the deviceto be cooled, but at least some fibres are light transparent andtransport light into the object to be cooled/heated;

[0177]FIG. 33 is an illustration of a capillary evaporator/condensersimilar to the heat exchanger of FIG. 5 but with a porous wall, whichpumps fluid to evaporate;

[0178]FIG. 34 is an illustration of a capillary evaporator/condenser inwhich the fibre members comprise a capillary structure attached to awall of the fibre heat exchange structure.

[0179]FIG. 35 is an alternative to an embodiment shown in FIG. 34, andin which a capillary structure is attached to a wall of the fibre heatexchange structure;

[0180]FIG. 36 is still an alternative to an embodiment shown in FIG. 34,and in which a porous media is attached to a different wall of the fibreheat exchange structure;

[0181]FIG. 37 is an illustration of a further alternative to anembodiment shown in FIG. 34 and in which a porous media is placedbetween walls of the fibre heat exchange structure, and vapour channelsplaced close to walls;

[0182]FIG. 38 is an alternative to an embodiment shown in FIG. 37, andin which a porous media is placed between the walls of the fibre heatexchange structure, and vapour channels placed inside the porous media.

[0183] A first embodiment of a heat exchange structure constructed inaccordance with one aspect of the invention is illustrated in a partialcross section in FIG. 1 of the accompanying drawings.

[0184] The heat exchange structure comprises a stack of plates 1,2,3made of woven fibrous material or any suitable material, as said in thetext of the invention, which define opposing walls of channels alongwhich fluid can flow. In FIG. 1 only three plates are shown which definetwo closed channels 4,5. The plates 1,2,3 could be rectangular in shapeand are encased within a housing (not shown) that defines the remainingwalls of the channels 4,5. Openings in the housing or the plates (notshown) allow fluid to enter and to exit from the heat exchanger.

[0185] The plates 1,2,3 are held in a spaced apart arrangement, whichcan be substantially parallel to the adjacent plate or plates. Eachplate 1,2,3 is constructed of a fibrous material and is produced byweaving or sewing together fibres or bundles of fibres, for example inthe form of tapes or strips to form a sheet. A stitching technique couldbe also used. However, walls could be made from any suitablematerial—resinous, plastic, metal, etc.

[0186] A plurality of continuous fibre members 6,7,8,9 (of which fourare illustrated in FIG. 1 extend through each of the plates 1,2,3 andhence the two channels. Each fibre member comprises an elongate fibre ofcarbon, silicon carbide or other material of suitable thermalconductivity. The fibres are aligned orthogonal to the plane of theplates and hence the flow of fluid through the channels. The concept“fibre” includes small diameter rods, plates, and ribbons.

[0187] In use, a fluid from which heat is to be extracted is passedalong one of the channels 4,5. A heat transfer fluid into which heatfrom the hot fluid is to be sunk is passed along the adjacent channel5,4. The fibre members 6,7,8,9 act to transfer heat by conduction alongthe fibres between the channels 4,5.

[0188] Of course, the heat exchange structure could be equally wellsuited to heating a fluid if a heat transfer fluid at an elevatedtemperature is used. Heat energy will then flow in the oppositedirection along the fibre members 6,7,8,9.

[0189] Because the fibres of the fibre members 6,7,8,9 penetrate throughthe walls of the channels, the efficiency of heat transfer is directlydependent upon the thermal conductivity of the fibre members and theirgeometry. The fibres can also directly carry stresses that are appliedalong their length. If the fibre members did not pass through theplates, they would need to be thermally bonded to the plates as in someof the prior arts. This produces a weaker and less efficient structure.

[0190] The fibre members 6,7,8,9 may be provided in a variety ofconfigurations and have a wide range of different cross-sections. FIG.14 is an overhead view of a set of fibre members illustrating some ofthe various possible spatial arrangements of the fibre members withinany of the heat transfer assemblies of the present invention.

[0191]FIG. 2 is a partial cross sectional view of a modification of theplate heat exchanger of FIG. 1. Where possible, like reference numeralshave been used to denote equivalent components. In this embodiment theplates and the fibre members are again woven together but are alsoimpregnated with a protective and reinforcing binding material 21. Thiscomprises suitable ceramics, and/or carbon, and/or metal, and/or apolymeric resin which provides additional reinforcement to the structureas well as protecting the fibres in the members from corrosive fluidsthat flow in the channels. Often, before an impregnation some additionalmaterials should be deposited on the fibre surface in order to protectfibres from the process of impregnation. Heat can pass through theprotective coating into the fibres for transfer from one channel toanother channel.

[0192]FIG. 3 illustrates a different fibre heat transfer structure. Inthe described embodiment the fibre members 6, 7, 8, 9 are crossing walls1, 2, 3 of the structure not orthogonally. The similar structure will beshown below in FIG. 9. The fibre members crossing walls at differentangles improve mechanical and thermal properties of the fibre heatexchange structure. The shown embodiment of the heat exchanger can bemade into a structural element of some machine, which provides greatversatility. For example, it could be used as a structural part of anaircraft body or wing, or perhaps of the body of a spacecraft. To usepart of a body or wing to act as a heat exchanger reduces the weight ofthe craft. Similar design could be used for structural materials, andmoreover, such structural materials could be cooled/heated and thusprovide a low thermal signature of crafts.

[0193] It will be readily appreciated that fibre members do not need topass orthogonally through the walls and the channels. For example, analternative arrangement is illustrated in FIG. 3 of the accompanyingdrawings which illustrates a fibre heat exchange structure in whichfibre members 6, 7, 8, 9 are inclined relative to the walls of the fibreheat exchange structure. This is a partial cross sectional view of anembodiment of a fibre heat exchange structure in which the fibres arenot orthogonal relative to the plane of the plates. Again only fourfibre members 6, 7, 8, 9 and three plates 1, 2, 3 are shown although inpractice many more may be provided.

[0194] In yet a further refinement, as shown in the embodimentsillustrated in FIG. 4 and FIG. 5 of the accompanying drawingsrespectively, the channels defined between the plates of a heatexchanger may incorporate baffles 14, 15 which increase the strength ofthe assembly. In FIG. 5 three parallel plates 1, 2, 3 defining twochannels are shown. The channels include baffles 14, 15 in the form of acorrugated or wavy sheet of fibrous or other material. The sheet extendsacross the width of the channel and is bonded or not bonded to the wallsof the channels at its crests and its troughs. Of course, it alsoenvisaged that the baffle may be formed by weaving or sewing fibres orsheets of fibrous material at the same time as the plates areconstructed to produce a stronger assembly. The bonding could, forinstance, be by way of a line of stitching.

[0195] In the alternative arrangement of FIG. 4, which is a perspectiveview of a further embodiment of the fibre heat exchange assembly, onlytwo plates 1, 2 are provided to define a single channel down which heattransfer fluid can be passed. A corrugated baffle 14 divides the singlechannel into sub channels 4, 5. A different fluid can be passed alongeach of these sub-channels if desired. If baffles of the fibrestructures shown in FIGS. 4 and 5 are porous then this is the embodimentshown in FIG. 11. Such embodiment can be used as the capillary thermalmanagement device. A working fluid can be supplied through capillarybaffles and take part in heat transfer either as a single phase or twophase working liquid. All embodiments shown in FIGS. 4, 5 and 11 alsocould be structural materials.

[0196]FIG. 6 illustrates a fibre member inside structure. In thisdrawing a cross section view of a fibre member is shown, which no longercomprise a single fibre strand/ligament but instead is comprised of anumber of fibre ligaments 22 in parallel which each pass through thechannels and the walls fibres and are encased in a protective 23 andbinding/matrix material 21 to form a composite structure. Each fibreligament 22 is provided with its own protective layer 23 in addition tothe final binding material 21. This construction allows fibre members ofvarying strengths, thermal parameters and cross sections to be produced.However, often a protection layer is not needed and only bindingmaterial—matrix is present. In the described manner the heat exchangercan be made into a structural element of some machine, which providesgreat versatility. For example, it could be used as a structural part ofan aircraft body or wing, or perhaps of the body of a spacecraft. To usepart of a body or wing to act as a heat exchanger reduces the weight ofthe craft. Similar design could be used for structural materials, andmoreover, such structural materials could be cooled/heated and thusprovide a low thermal signature of crafts.

[0197]FIGS. 7 and 8 illustrate a cross sectional view of the embodimentsimilar to shown in FIGS. 4 and 5, but with fibre members 6, 7, 8, 9 notorthogonal to walls, as it is shown in FIG. 3, and one of the structuralelements 14, 15 filling the entire space between walls 1, 2. Only onestructural member 15 is installed in the fibre structure of FIG. 7, andtwo structural members 14, 15 are installed into the fibre structureshown in FIG. 8. The structural member 15 in FIGS. 7 and 8 could becomprised from plastic materials or other materials includingporous/fibrous. In this case the embodiments can be used as thecapillary thermal management devices. All embodiments shown in FIGS. 4,5 and 11 also could be structural materials.

[0198] A further embodiment of a fibre heat exchange structure inaccordance with the present invention is shown in the cross sectionalview of FIG. 9. In this embodiment the fibre members are grouped intotwo groups. A first group of fibre members 6, 7 subtend an acute angle(A) with one wall of a channel whilst the second group 8, 9 subtend anobtuse angle (180+A). The fibre members of each group are arranged inseveral rows of evenly spaced fibre members to criss-cross the channels.

[0199]FIG. 10 is a perspective view of part of the fibre heat exchangestructure illustrated in FIG. 9. From this figure the relative locationof the fibre members can be clearly seen.

[0200]FIG. 11 is a perspective view of the structure similar to thefibre heat exchange structure illustrated in FIG. 4. The difference isthat the baffle of the fibre structures shown in FIG. 11 is porous. Thisembodiment can be used as the capillary thermal management device. Aworking fluid can be supplied through the porous/capillary baffle andtake part in heat transfer either as a single phase or two phase workingliquid. The embodiment shown in FIG. 11 also could be the structuralmaterial.

[0201] Although the plates defining the walls of the channels of theabove described and illustrated heat transfer assemblies are planar, itis possible to construct a heat transfer device in other configurations.

[0202] As shown in FIG. 12 of the accompanying drawings, which is across sectional view of an embodiment of a fibre heat exchangestructure, three cylindrical plates 1, 2, 3 may be provided. The plates1, 2, 3 are nested one inside the other around a common axis to definetwo closed walled channels 4, 5. Fin shaped fibre members 6, 7 extendradially through the walls and axially along the channels to form aregular structure. It is envisaged that such a construction will findapplication in the cooling/recuperating of exhaust gas that has passedthrough a gas turbine. For instance, the turbine (not shown) may belocated within the innermost cylindrical plate 1 to produce a compactassembly. Again, because the fibre members pass through the walls andthe channels efficient heat transfer and improved stress properties canbe achieved.

[0203] A further embodiment of a fibre heat exchange structure inaccordance with the present invention is shown in the cross sectionalview of FIG. 13. In this embodiment the corrugated fibre structuralmember/baffle is installed into the channel space between cylindricalwalls 1, 2 subdividing this channel space into a number of sub channels.The fibre members are grouped into several groups, and only three groupsare shown. A first group of fibre members 6, 7 subtend an acute angle(A) with one wall of a channel whilst the second group subtend an obtuseangle (A+ some angle). The third group has an additional angle shift.Thus, the efficiency of the heat exchange structure can be improvedwhilst geometry of channels is convenient for fluid connections.

[0204]FIG. 14 shows different geometry of fibre members distributioninside channels, which have a drastic effect on the fibre heat exchangestructure pressure drop and effectiveness.

[0205]FIG. 15 shows the evolution of the fibre heat exchange structure(a) into a heat sink with partial cross sectional views of an embodimentof a heat sink (b) in accordance with the present invention bonded to anobject 12 to be cooled or heated and with an embodiment of a heat sink(c) with an object 16 to be heated/cooled deposited on a wall;

[0206]FIG. 12 is a partial cross sectional view of a first embodiment ofa heat sink in accordance with the present invention bonded to an object12 to be cooled or heated. The heat sink 120 comprises a pair of spacedapart, planar, parallel plates 1, 2 which define opposing sides of achannel along which heat transfer fluid can be passed. As describedhereinbefore a plurality of fibre members 6, 7, 8, 9 are provided whichpass through the two plates 1, 2 and hence the channel. One end of eachof the fibre members 6, 7, 8, 9 is placed in thermal contact with anobject 12 to be heated or cooled. The fibre members 6, 7, 8, 9 then actto dissipate heat from the object 12 to fluid in the channel.

[0207] In another embodiment, the invention may provide an electronicdevice or component in which heat conducting fibres are embedded withinthe device to be cooled or surround the device to be cooled.

[0208] As shown in the embodiment of FIG. 17, which is a cross sectionalview of a first embodiment of a combined electronic device and the fibreheat exchange structure. An object to be cooled/heated embeds within theends of a number of fibre members 6, 7, 8, 9. In the figure, four suchmembers are shown although in practice many more can be provided. Asingle plate 1 is provided which lies in parallel with the surface ofthe device to be cooled/heated from which the fibre members protrude.This defines a single fluid receiving channel 5 between the plate 1 andthe device. The fibre members 6, 7, 8, 9 extend across the channel andthrough the plate 1. Thus, heat from the circuit can pass along thefibre members 6, 7, 8, 9 for dissipation into the fluid in the channel.

[0209] Various modifications to the assembly of FIGS. 16 and 17 can ofcourse be made within the scope of the present invention. In some cases,it may be necessary or desirable to electrically isolate the fibres fromthe object. This may be necessary where the fibres are electricallyconductive such as carbon or graphite fibres. For example, as shown inFIG. 18 the ends of embedded fibre members 6, 7, 8, 9 are covered withelectrically insulting material 24. As shown in FIG. 19 of theaccompanying drawings, an electrical insulating layer 24 can be providedbetween the heat sink wall/substrate 2 and the object 12 to be heated orcooled. The ends of the fibre members are thermally in contact with theelectrical insulation layer 24, and may be embedded in the layer ifrequired. Also, as it is shown in FIG. 20, three fibrous plates 1, 2, 3defining two parallel channels could be provided. More than two channelsare also envisaged, and each one may be adapted to carry a differentheat exchange fluid. FIG. 26 is a further modified fibre heat transferassembly in which the walls 1, 2 of the heat transfer assembly and thefibre members 6, 7, 8, 9 are covered with electrically insulatingmaterial.

[0210]FIG. 22 is a perspective view of part of the fibre heat exchangestructure illustrated in FIG. 19. From this figure the relative locationof the fibre members and the electrical insulation layer can be clearlyseen.

[0211] Other heat transfer assemblies are envisaged. For example, FIG.23 is an illustration of a three dimensional micro-electronic circuitwith the integral cooling fibre heat exchange structure in accordancewith one aspect of the invention.

[0212] The assembly of FIG. 23 comprises two parallel spaced apartfibrous plates 1, 2, which define a channel along which cooling fluid,such as air, can flow. Fibre members 6, 7, 8, 9 extend through the wallsof the plates and the channel. A part of the fibre members 6, 7, 8, 9(four are shown) surface provides a support for a respectivethree-dimensional integrated circuit 25.

[0213] In another embodiment, the invention may provide an electronicdevice or component in which heat conducting fibres are embedded withinthe device to be cooled or surround the device to be cooled. Althoughnot shown in the drawings, the fibres could encase one or more, andpreferably all sides of the device to provide a shield that protects thedevice form external electromagnetic radiation fields. This isespecially advantageous if electrically conductive fibres are used whichcan be earthed to a suitable earth point.

[0214]FIG. 24 is an illustration of a micro-electronic circuit 12integrated with a heat sink defined by two walls 1, 2 and fibre members6, 7, 8, 9. The microchip is protected by fibre members 6, 7, 8, 9 fromEMI in accordance with one aspect of the invention. FIG. 32 illustratesthe heat sink defined by walls 1, 2, the heat conducting fibre members6, 7, 8, 9 and optical fibre members 32 integrated with the microchip12. The light source 31 provides special frequency light to heal themicrochip from radiation damage.

[0215] An alternative embodiment of a heat sink assembly, againincorporating many features of the embodiments of FIGS. 1 to 24 is shownin FIGS. 25 to 27 of the accompanying drawings.

[0216] The shown heat sink comprises a hollow cylindrical tube 1 throughwhich heat exchange fluid can be passed. A plurality of fibre members 6,7 pass through the cylinder and the cylinder walls. One end of each ofthe fibre members 6, 7 passes through the cylinder 1 in the location ofa first area of the cylinder which, in use, is adjacent the object 12 tobe cooled/heated. The opposite end of each member 6, 7 passes throughthe cylinder wall at a different point. As shown, the fibre members 6, 7and the wall 1 form a substrate originating at the first area.

[0217] As shown in FIG. 25 and FIG. 27 of the accompanying drawings thefibre members may comprise linear members such as rods or plates made upof one or more fibres. Alternatively, the fibre members 6, 7 may bestepped so as to present a greater area of fibre member within thecylinder.

[0218] An electric fan 17, shown in FIG. 27 but omitted from FIGS. 25and 26 of the accompanying drawings is attached to one end of thecylinder to blow fluid along the channel. In use, the heatsink/substrate is attached to a device such as an electronic circuitformed as a chip, which is to be cooled. The said microchip could beintegrated with the heat sink. Power for the fan can then be providedfrom contacts provided as a part of the substrate for the electroniccircuit.

[0219]FIG. 28 is an illustration of an embodiment of atransmitter/receiver for light or other forms of electromagneticradiation. The fibre assembly comprises a plurality of fibre members 6,7 which extend from a transducer/generator 1 and which includecontinuous fibres along which the radiation can be propagated. Each ofthe fibre members 6, 7 is deliberately charged with an electricalpotential which aligns the fibres. In the example shown, the fibremembers comprise single carbon fibres, which all have an electricalcharge and so repel one another to produce spaced fibre members assemblywhich fan out from the transducer. A number of layers of fibre memberscan be provided.

[0220] In alternative embodiment FIG. 29 fibre members 6, 7 have bondedtogether ends. If charged they produce the bottle shape structure, whichcan be used similar to FIG. 28 embodiment.

[0221]FIGS. 30 and 31 illustrate modifications of a fibre heat transferassembly (such as a heat sink or heat exchanger) in which one or more ofthe plates or the fibre members are connected to a source of electricalpotential to improve heat exchange by an electrical field interactionwith a fluid dipoles or/and by an interaction between free charges andmolecules. FIG. 30 illustrates such a modified fibre heat transferassembly in which the fibre members 6, 7, 8, 9 that pass through thechannels are electrically charged; and FIG. 31 is a further modifiedfibre heat transfer assembly in which the walls 1, 2, 3 of the fibreheat exchange assembly are electrically charged instead of the fibremembers 6, 7, 8, 9.

[0222]FIG. 33 is an illustration of a heat transfer assembly with acapillary wall. The heat transfer assembly is comprised of liquid 5 andvapour 4 channels reinforced with structural members 14, 15. Thechannels are separated by a capillary wall 2. The entire assembly ispenetrated by fibre members 7, 8, which hold the structure from internalpressure. Heat absorbed by the assembly through wall 1 will be spread bythe wall and then conducted through fibre members 6, 7 and structuralmember 14 to the porous wall 2. Liquid supplied through a liquid channel5 will evaporate on the surface of contact between fibre 6, 7,structural 14 members and the porous wall 3. The structural members 14and 15 in this assembly are used for structural support and to conductheat from wall 1 to porous wall 2.

[0223]FIG. 34 is an example of a single channel capillary cooling devicethe object of heating/cooling 12 attached to the wall 1.

[0224] It is appreciated that most of the devices presented in thispatent can work in heating or cooling mode. In the case of a two-phasedevice such as the capillary pump devices in the heating mode, thecondensation will occur on the elements of the heat transfer assemblyand the capillary structure will pump liquid from the condensation areainstead of supplying liquid into the evaporating area. Simplified, justthe cooling (evaporating) mode is described; however, these devices canwork as well in heating (condensing) mode.

[0225] The channel wall 1 is penetrated by fibre members 6, 7, 8, 9 orit can be comprised from the fibre members. These members are extendedinto the channel and transfer heat from the object of heating/cooling 12into the channel 4. The fibre members 6, 7, 8, 9 are located closeenough to form the capillary structure which is pumping cooling liquidthrough the fibrous structure. The evaporation or cooling fluid coolsdown the fibre members and through them the object of heating/cooling.

[0226] In FIG. 35, the additional fibrous structure 14 is inserted intothe channel 4 of the heat transfer assembly. This structure canreinforce the heat transfer assembly and act as a structural member 14,or it can form the wall 1 of the heat transfer assembly, and be attachedto the object of heating/cooling 12. Cooling liquid is supplied throughthe capillary structure and evaporates on the fibre members 6, 7, 8, 9.The rest of the channel is used for vapour circulation. This additionalcapillary structure forms the wall connected to the object ofheating/cooling.

[0227] In FIG. 36, the additional fibrous structure 14 is inserted intothe channel 4 of the heat transfer assembly. It is attached to the wall2 of the channel 4. This structure can reinforce the heat transferassembly and act as a structural member 14, or it can form the wall 2 ofthe heat transfer assembly. Cooling liquid is supplied through capillarystructure and evaporates on the fibre members 6, 7, 8, 9. The rest ofthe channel is used for vapour circulation. The vapour channel preventsdirect conduction of heat from the wall to the porous structure.

[0228] In FIG. 37, the additional fibrous structure 14 is inserted intothe middle of channel 4 of the heat transfer assembly. It separates theliquid and vapour channels. This structure can reinforce the heattransfer assembly and act as a structural member 1. Cooling liquid issupplied through the liquid channel 5, and the capillary structure 14and evaporates on the fibre members 6, 7, 8, 9. The rest of the channelis used for vapour 4 circulation. The vapour channel prevents directconduction of heat from the wall to the porous structure.

[0229] In FIG. 38, the additional fibrous structure 14 occupies theentire space between the channel walls 1 and 2. Vapour channel 4 isformed inside the capillary structural member 14. It can be formed closeto one or the other wall of the channel or close to the fibre member oraway from it. Heat is conducted through fibre members 6,7,8,9. Thecooling fluid is evaporated through the capillary structure 14 andcirculated through vapour channel 4.

1. A heat transfer assembly which comprises at least one wall which isadapted to separate a first fluid at a first temperature from a secondfluid at a second temperature, and at least one fibre member orplurality of them, each fibre member including at least one elongatefibre which extends substantially axially along the fibre member fromthe first fluid through the wall and into the second fluid whereby inuse heat is transferred from the first fluid to the second fluid or viceversa, and the entire heat transfer assembly or a part of it isassembled as a single unit by sewing/weaving/stitching technique.
 2. Aheat transfer assembly according to claim 1 in which the first andsecond fluids are received within respective first and second channelsprovided on opposing sides of the wall.
 3. A heat transfer assemblyaccording to claim 1 in which a stack of substantially parallel platesdefining walls is provided with a channel being defined between adjacentwalls.
 4. A heat transfer assembly according to any preceding claimwhich comprises a heat exchanger.
 5. A heat transfer assembly accordingto any preceding claim in which the first and second fluids comprisedifferent fluids.
 6. A heat transfer assembly according to any precedingclaim in which each fibre member comprises at least one fibre, which isconsisted from at least one ligament or plurality of them, or a numberof fibres to form a fin or other structural element which adds to therigidity of the finished structure.
 7. A heat exchanger according to anypreceding claim which is entirely fabricated from fibres that are wovenor sewn together.
 8. A heat exchanger according to claim 7 in which saidentire fibre structure is impregnated with a matrix material.
 9. A heattransfer assembly comprising a device to be cooled or heated, one ormore walls defining at least one channel and one or more fibre memberswhich extend through the wall or walls from the heat source to thechannel whereby in use heat from the object to be cooled is transferredthrough the wall and through the fibre members into the channel, andvice versa—heat from the channel is transferred through the fibremembers and through the wall to the object to be heated up.
 10. A heattransfer assembly according to claim 9 in which the object to be cooledcomprises a hot fluid or other heated body.
 11. A heat transfer assemblyaccording to claim 9 or claim 10 in which the object to be cooled orheated up comprises an electronic circuit.
 12. A heat transfer assemblyaccording to claim 9 or claim 10 in which the object to be cooled ismounted on a substrate which comprises a wall of the heat transferassembly, or at least one or plurality of fibre members, or a wall andone or plurality of fibre members together.
 13. A heat transfer assemblyin which an electronic circuit is provided on a substrate according toclaim 12 which is attached to at least one or plurality of fibre membersextending therefrom through which heat generated by an electroniccircuit can be dissipated.
 14. A heat transfer assembly according to anyone of claims 9-13 in which one or more electronically insulating layersare inserted between the substrate and an object to be cooled or heatedup.
 15. A heat transfer assembly according to any one of claims 10-14 inwhich the material of the substrate has substantially the samecoefficient of expansion as the circuit to be cooled.
 16. The heattransfer assembly of any one of claims 9-14 in which the substratecomprises at least one or plural fibre members.
 17. The heat transferassembly of any one of claims 13-16 in which the material of the objectto be cooled or heated is deposited directly onto the substrate attachedto the fibre members or onto fibre members, which can be at least onefibre or ligament
 18. The heat transfer assembly of any one of claims13-17 in which the material of at least one fibre member or plurality offibre members is a semiconductor.
 19. A heat transfer assembly accordingto any one of claims 13-18 in which one or more fibres of the fibremembers are optically conductive and light can be transmitted into orout of electronics circuit
 20. A heat transfer assembly of any one ofclaims 13-19 in which one more of the fibres of the fibre members areelectronically conductive and encase, either wholly or partially theobject to be cooled or heated up.
 21. A heat transfer assembly accordingto any preceding claim in which the walls are made from electricallynon-conductive material and each of selected ones of the fibre membersare made of electrically conductive material or are covered withelectrically conductive material, and has an electrical charge appliedto it/them
 22. A heat transfer assembly according to any preceding claimin which the walls are made of electrically conductive material whilstthe fibre members are electrically non-conductive, and walls areelectrically charged.
 23. A heat transfer assembly such as a heat sink,comprising a hollow body having first and second open ends, an outersurface and an inner surface and which is provided with a plurality offibre members that extend generally from a first interior surface of thebody across the interior of the body to contact the interior surface ofthe body in a different area, and in which the body is adapted tocontact the device to be cooled substantially at the first area so thatthe fibre members are in thermal contact with the device to be cooled.24. The assembly of claim 23 in which a fan is provided which isattached towards one end of the hollow body.
 25. Apparatus according toany preceding claim in which one or more of the fibre members includesurface perforations or depressions.
 26. Apparatus according to anypreceding claim in which one or more of the fibre members surface isenhanced and improved for improved heat transfer and/or boilingnucleation purposes by any means including but not limiting to chemicaltechnologies.
 27. Apparatus according to any preceding claims in whichone or more of the fibre or non-fibre members is adapted to form atleast on capillary.
 28. Apparatus according to any preceding claim inwhich the or each wall, structural member, or fibre member of the heattransfer assembly comprises a capillary structure.
 29. Apparatusaccording to any one preceding claim in which the fibre members compriseat least one or plurality of threads/ligaments which are woven,threaded/sewn or/and bonded together.
 30. A heat transfer assemblyaccording to any preceding claim in which walls are of annular form. 31.Apparatus according to any preceding claim in which the or each wallcomprises a woven/sewn sheet of fibres/ligaments.
 32. A heat transferassembly for a gas turbine or the like in which the heat transferassembly is in accordance with any one of the preceding claims and hasat least three concentrically arranged walls; a first inner wall, anintermediate wall and a second outer wall defining at least two annularchannels therebetween that surrounds at least a part of the entire gasturbine, one or more of the fibre members passing through theintermediate wall to transfer heat energy from fluid within the onechannel to fluid inside the other channel.
 33. A heat transfer assemblyaccording to claim 32 in which an additional wall is provided which isconcentric with the outer wall and which is adapted to define a furtherchannel that may receive fluid such as water, and heat energy extractedfrom the exhaust gas being used to heat the water.
 34. A heat transferassembly according to claim 30, 31 or 32 in which the cylindricalchannels are subdivided into smaller channels by a fibre structuralmember or baffle, and at least one or plurality of fibres penetratewalls and/or structural fibre member/baffle transferring heat energybetween channels.
 35. A gas turbine or other engine incorporating a heattransfer assembly according to any one of the claims 30 to
 34. 36.Apparatus according to any preceding claim in which the fibre membersare impregnated with a binding material to form a composite structure.37. Apparatus according to claim 36 in which binding material is addedto the fibres to produce the final composite assembly using thetechnique or mixture of techniques.
 38. Apparatus according to anypreceding claim in which fibre surfaces of fibre members are coated byone or more coatings.
 39. Apparatus according to preceding claim 38 inwhich the fibre surfaces of fibre members are coated by one or moreprotective coatings of metal.
 40. Apparatus according to any precedingclaim in which the fibre members extend through the walls substantiallyorthogonal to the walls.
 41. Apparatus according to any one of thepreceding claims in which the fibre members and the wall define anobtuse or acute angle
 42. Apparatus according to any preceding claimwhich further includes a reinforcing baffle which comprises a wavy sheetthat is provided between the opposing walls of the channel and fixed toone wall at its crests and to the other wall at its troughs. 43.Apparatus according to claim 42 in which the reinforcing baffle isfabricated from porous, fibrous or solid matter and occupies one or morechannels.
 44. Radiation heat and other radiation energy conversion andguiding assemblies comprising a substrate having at least two orplurality of fibre members extending therefrom in which each fibremember comprise one or plurality of fibre/ligaments of a special naturewhich are adapted to guide energy from one end of the fibre to the otherend of the fibre, and/or to convert energy, to the most part, on thesurface of the fibres, and control means for applying an electricalcharge to the fibre members to control the direction and/or angle inwhich the energy is transferred.
 45. Radiation heat and other radiationenergy guiding/converting assembly according to claim 44 in which eachfibre member has a surface layer which is adopted to improvereflection/conversion of energy on/from the surface.
 46. Radiation heatand other radiation energy guiding/converting assembly according toclaim 44 in which each fibre member has a surface layer which is adoptedto convert radiation energy incident upon the surface of the fibremembers into electrical energy.
 47. Radiation heat and other radiationenergy guiding/converting assembly according to claim 44 which includesfibre members which have optical transparency to guide light in thedirection of each such member.